Exam 4

Nervous and senses

what is the function of the nervous system?

detects changes, makes decisions, stimulates muscles and glands to respond, and maintains homeostasis

what does the sensory division of the nervous system do?

receives information, utilizes sensory receptors, relays information to the CNS

motor response division

" to move", "decision" into action, impulses are carried to effector

neurons are names by

the number of extensions radiating from cell bodies

what are the two division of the motor division?

somatic and autonomic nervous system

what does the somatic nervous system do?

transmits voluntary instructions to skeletal muscle

What does the autonomic nervous system do?

transmits involuntary instructions to smooth muscle, and cardiac muscle. and glands

_______ is a type of glial cell

schwann cell

________- encases peripheral axons in a sheath of lipoprotein

myelin

the coating of the schwann cell is called the

myelin sheath

gaps between myelin clusters are called

nodes of ranvier

myelin helps to increase the conduction velocity of a

nerve impulse

Are all axons myelinated?

no

unmyelinated PNS axons are encased by the __________

Schwann cell cytoplasm

neurons are named by

the number of extensions radiating from cell body

99% of neurons, many processes, most neurons of the CNS

multipolar neurons

two processes, associated with special senses (eyes, ears, and nose)

bipolar neurons

one process, cell bodies are in ganglia, sensory

unipolar neurons

afferent neurons, carry impulses to CNS, some are bipolar

sensory neurons

links neurons together, multipolar, located within the CNS

interneurons

efferent, multipolar, carry impulses away from the CNS, deliver signal to effectors

motor neurons

what are the 5 roles of the neuroglia?

1. provide support for neurons,

2 guide embryonic neurons into position,

3 produce growth factors to nourish neurons ,

4

clears excess ions and neurotransmitters,

5 assists in formation of synapses

connects neruons to blood vessels, exchange nutrients and growth factors, form scar tissue, regulate ion concentration, part of the BBB

astrocytes

myelinated CNS axons, provides structural support

oligodendrocytes

phagocytic cell, and provides structural support

microglia

lines central canal of spinal cord, lines ventricles of the brain, regulates composition of cerebrospinal fluid, has ciliated/columnar cells

ependyma

what are the two neuroglia of the PNS?

Schwann cells and satellite cells

produce myelin sheath found on some peripheral axons and speeds up nerve impulse transmission

Schwann cell

support clusters of neuron cell bodies

satellite cells

the resting membrane potential is the potential difference in charge across the

axon membrane

_______ is the potential difference from inside to the outside of the cell

70mV

the inside of a cell is

negative

the resting membrane is said to be a

polarized membrane

neurons are ______ cells

excitable

detect stimuli and respond by changing their ________

resting potential

the common response is the opening of a gated ion channel that results in the membrane becoming less negative which is considered

depolarized

if depolarization reaches the _____ of -55 mV, an action potential results

threshold potential

what is the number that causes an action potential

-55 mV

an action potential is an

all or none response

if a neuron axon responds at all it responds ______ - with an action potential

completely

a nerve impulse if conducted whenever a stimulus of ______ ____ or above is applied to an axon

threshold intensity

all impulses carried on an axon are the _____-

same strength

stimulus of greater intensity produces _______ of action potentials, not stronger impulses

higher frequency

during an impulse, the portion of an aaxon actively conducting the action potential is not able to respond to another threshold stimulus at normal strength. This is called:

refractory period

what are the two types or refractory periods?

absolute and relative

time when threshold stimulus cannot generate another action potential, voltage-gated NA+ channels are briefly unresponsive

absolute refractory period

time when only high-intensity stimulus can generate another action potential, repolarization is not complete and membrane is re-establishing resting potential

relative refractory period

the speed of impulse conduction varies with

myelination

myelinated axons transmit through ___, in which action potentials "jump" from node to node down the axon

saltatory conduction

saltatory conduction is much ___ than impulse conduction in unmyelinated axons

faster

______ also affects conduction speed; thick axons transmit faster than thin axons

axon diameter

120 m/sec

thick, myelinated axons

0.5 m/sec

thin, unmyelinated axons

where does the spinal cord begin?

foramen magnum

the spinal cord extends downward through the _________

vertebral canal

the spinal cord terminates at the _____ and ______ lumbar vertebrae space

L1 and L2

the spinal cord is comprised of ______ segments which branches into a pair of spinal nerves

31

a ___ is an automatic, subconscious response to stimuli within or outside the body

reflex

a ____ is a neural pathway that consists of sensory receptor + 2 or more neurons + and effector

reflex arc

what is the most common reflex arc

sensory neuron, interneurons, motor neurons

monosynaptic= only 1 synapse, consists of 2 neurons: sensory and motor

monosynaptic (stretch) reflex

what occurs when you touch or step on something painful

withdrawal reflex

the ___ helps prevent tissue damage by removing limb from source of injury

withdrawal reflex

the withdrawal reflex is ______ in that the pathway involves 3 neurons ( and thereby 2 synapses

polysynaptic

activation or pathway results in reciprocal innervation:

flexors contract, extensors are inhibited

_______ occurs when flexors on the affected side contract, and extensors on the contralateral side also contract to stabilize the body during withdrawal reflex

crossed extensor reflex

crossed extensor reflex helps

shift body weight to ensure you do not fall

----- are spinal cord pathways composed of axons

tracts

___ _____ conductor sensory impulses to the brain

ascending tracts

_____ ________- conduct motor impulses from the brain to motor neurons reaching muscles or glands

descending tract

if the word has "spinal" in it, it is a ___ tract

decending

name the 4 ascending tracts

fasciculus gracilis, fasciculus cuneatus, spinothalmic tracts, spinocerebellar tracts

name the 3 descending tracts

corticospinal tracts

the PNS is divided into two what categories?

somatic and autonomic nervous system

conduct impulses into the brain or spinal cord

sensory nerves

conduct impulses to muscles or glands

motor nerves

contain both sensory and motor nerve fibers

mixed nerves

most nerves are ____ nerves

mixed

all spinal nerves are mixed, except

the first pair

name the 4 subdivisions of cranial and spinal nerves

general somatic efferent fibers, general visceral efferent fibers, somatic afferent fibers, and general visceral afferent fibers

carry motor impulses from the CNS to skeletal muscle

general somatic efferent fibers

carry motor impulses from the CNS to smooth muscles and glands

general visceral efferent fibers

carry sensory impulses to the CNS from skin and skeletal muscles

general somatic afferent fibers

carry sensory impulses to the CNS from blood vessels and internal organs

general visceral afferent fibers

_____ fibers are associated with specializes structures, and are found in only cranial nerves

special

carry motor impulses from the brain to the muscles used in chewing, swallowing, speaking, and forming facial expressions

special somatic efferent fibers

carry sensory impulses to the brain from olfactory and taste receptors

special visceral afferent fibers

carry sensory impulses to the brain from receptors of sight, hearing, and equilibrium

special somatic afferent fibers

all spinal nerves originate from

spinal cord

how many pairs of spinal nerves are there

31

how many cervical nerves are there

8

how many thoracic nerves are there

12

how many lumbar nerves are there

5

how many sacral nerves are there

5

how many coccygeal nerves are there

1